[Discuss-gnuradio] Aliasing Question

From:

jonshan

Subject:

[Discuss-gnuradio] Aliasing Question

Date:

Tue, 10 Jul 2007 19:47:15 -0400 (EDT)

User-agent:

SquirrelMail/1.4.8

Hello,
I don't know if this is intended behavior or not.
I am running ./usrp_siggen -f10e6 -w150k -i256
At the receiver, I am running ./usrp_fft.py with -f9.8e6, -d128
I see a peak at -150k.
According to my calculations,
(10e6 + 150k) - 9.8e6 = 350k. This is outside the Nyquist interval (-250k,
250k). Thus it gets aliased: 350k - 500k = -150k. Which seems to explain
the peak.
However, is this intended behavior? The magnitude (20dB) of the peak is
smaller than usual, compared to when I set center freq to 10e6 (>45dB). I
am uncertain.
Thanks,
Jonathan Shan